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We're now less than an hour away from Apple's (Nasdaq: AAPL) big iPhone 5 event. Let's look at one under-the-hood spec that doesn't typically get much attention, but is very significant when it comes to the new device's performance: the processor.

Apple's chip strategy has been evolving of late, branching out its A-family of custom ARM Holdings-based (Nasdaq: ARMH) processors into specialized uses. The third-generation iPad carries an A5X chip, which features two ARM Cortex A9 cores coupled with quad-core PowerVR graphics.

This chip is built on Samsung's 45-nanometer manufacturing process, which is relatively larger than ARM chips found in competing devices. For comparison, NVIDIA's (Nasdaq: NVDA) quad-core Tegra 3 uses a 40-nanometer process, while Qualcomm's (Nasdaq: QCOM) newest Snapdragon S4 chips have moved down to 28-nanometer.

Don't expect the A5X to be found in the iPhone 5. That chip's graphics capabilities are probably overkill for the iPhone 5, even with its taller screen. The third-generation iPad has 3.1 million pixels to drive its resolution of 2,048 x 1,536. The iPhone 5 is expected to have less than 730,000 pixels at a resolution of 1,136 x 640, or less than a quarter of the new iPad's.

For this reason, I expect Apple to focus more on the CPU side with the iPhone processor, because a smartphone simply doesn't need that much graphics horsepower compared to a tablet.

There's a good chance that the A6 -- or whatever it's called -- is built on Samsung's 32-nanometer process, moving down the scale in order to enjoy power efficiency gains and improved battery life. Apple did something clever behind the scenes earlier this year: It quietly moved down to 32-nanometer chips in products with lower unit volumes, presumably as a safer testing ground for the process.

The $399 iPad 2 that Apple released alongside the new iPad quietly made this change under the hood, and subsequently reaped a huge gain in battery life. Even though the iPad 2 was identical on the outside and the change was invisible to the user, its performance was actually improved. The current Apple TV also uses a single-core A5 built on 32-nanometer. Contrary to years of speculation, it doesn't appear that the iPhone maker is switching to Taiwan Semiconductor Manufacturing (NYSE: TSM) any time soon.

My official guess is that Apple might move up to a quad-core CPU built on a 32-nanometer process, dub it the A6, and call it a day.

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